Actuator for a switch



United States Patent 3,532,003 ACTUATOR FOR A SWITCH Junji Ohno,Hamamatsu-shi, Japan, assignor to Nippon Gakki Seizo Kabushiki Kaisha,Hamamatsu-shi, Shizuoka-ken, Japan Filed Oct. 14, 1968, Ser. No. 767,251Int. Cl. F16h 21/00 U.S. Cl. 74108 2 Claims ABSTRACT OF THE DISCLOSUREAn actuator for a switch, such as a keyboard switch in an electronicmusical instrument, having a resilently mounted actuating member whichperforms a translational movement. The switch actuator has a baseportion secured on a frame, a first resilient member projecting forwardfrom the base and a second integral resilient member extendingrearwardly from the free end of the first member. The first and secondmembers are proportioned in length, second moment of area and Youngsmodulus so that the actuating member mounted on the free end of thesecond member performs the desired translational movement.

The present invention relates to an actuator for a switch and, moreparticularly, it relates to an actuator for a keyboard switch of anelectronic musical instrument.

It is an object of the present invention to provide an actuator whichcan be advantageously used in a switch having a plurality of movablecontacts arranged in a juxtaposed relationship with respect to eachother in a relatively narrow space in a switch box, such as a keyboardswitch of an electronic musical instrument.

In accordance with the present invention there is provided an actuatorfor a switch in which an actuating member is resiliently supported so asto perform a translational movement, with a simple construction.

The invention will be explained with reference to the accompanyingdrawings in which:

FIG. 1 is a side view of actuators embodying the present invention;

FIG. 2 is a bottom plan of the actuators shown in FIG.

FIGS. 3a, b, c and d are diagrammatic views illustrating the principleof the present invention;

FIG. 4a is a vertical sectional view of the actuator shown in FIG. 1,and FIG. 4b is a sectional view similar to FIG. 4a shown in thedepressed state; and

FIG. 5 is a side view of a keyboard switch of an electronic musicalinstrument including the actuators shown in FIG. 1.

Referring to the drawings, an actuator for a switch according to thepresent invention comprises a base portion 2 adapted to be fixed to asuitable frame by means of a screw or the like, a first resilient member3 extending forward from said base portion, a second resilient member 4folded back from the forward end of said first resilient member and anactuating member 5 fixed at the free end of said second resilientmember, said first and second resilient members being so proportioned inlength, second moment of area and Youngs modulus that said memberperforms a translational movement. The second moment of area isdetermined by the cross sectional configuration such as width andthickness of each of the resilient members and the Youngs modulus isdetermined by the material thereof.

Now the principle of the present invention will be explained withreference to FIG. 3. FIGS. 3a, b and 0 diagrammatically show an actuatorhaving a first resilient member 3 and a second resilient member 4 whichare formed as an integral piece of uniform material having uniformthickness and width. The first resilient member 3 is fixed at its baseend, while the second resilient member 4 is provided at its free endwith an actuating member 5, to which a switch actuating force isapplied. In FIG. 3a, is a distance between the point of force A and thepoint of the forward end of the first resilient member B, is a distancebetween the point of force A and the point of the fixed end of the firstresilient member C and W is a force applied to the point of force A.FIG. 3b shows a stress distribution in the resilient mernbers caused bythe force W, and FIG. 3c shows a deflection of the resilient members. InFIG. 30, 0 is an angle of deflection of each of the resilient membersbetween the points A and B 6 is an angle of deflection of the firstresilient member between the points A and C. The angles 0 and 0 can beexpressed by the following equations:

where E is a Youngs modulus of the resilient member, and I is a secondmoment of area of the resilient member.

Thus the second resilient member at the point A is always maintained ina horizontal plane of the relation 20 =0 exists. This is,

2 WI1 W12 2E1 2EI where I is a second moment of area at the part of 1 ofthe resilient members (at the part of 1 the total width of the firstresilient member is equal to the width of the second resilient member,that is and I is a second moment of area at the part of (it is assumedthat part of 1 has a uniform width b) If 202562,

Accordingly, when the condition l /5l is satisfied, the second resilientmember is always maintained in a horizontal plane at the point to whichthe switch actuating force is applied and thus the actuating memberperforms a translational movement.

The same result will be obtained by properly selecting the distributionof the second moment of area or the Youngs modulus, such as by varyingthe width, thickness or material of the respective resilient members.

FIG. 1 shows an actuator embodying the above principle of the presentinvention. In the form shown in FIG. 1 the first resilient member 3 isrelatively thick at its intermediate portion so that the resilientdeformation occurs principally at its end portions. The second resilientmember 4 is integrally connected with the first resilient member 3.FIGS. 4a and b illustrate in cross section the operation of saidactuator, FIG. 4a showing the state where the actuating member has notbeen depressed and FIG. 4b showing the state where the actuating memberis depressed.

FIG. 5 is a side view of a keyboard switch including the actuatorconstructed in accordance with the present invention, in which is a keypivotally mounted at the backward end thereof, 11 is an actuatoraccording to the present invention, 12 is a movable wire contact adaptedto be actuated by said actuator and 13 is a fixed bus-bar contact. Whenthe key 10 is depressed the actuator is urged downward to move themovable wire contact 12 into contact with the fixed bus-bar contact 13.

It will be apparent from the above description that in accordance withthe present invention the translational movement of the actuator can beeasily obtained by properly selecting the length, the width, thethickness and the material of the first and second resilient memberswhich resiliently support the actuating member. The actuator is verysimple and compact in construction and can be manufactured at low cost,and consequently it can be conveniently adapted in a switch including aplurality of switch contacts arranged in a juxtaposed relationship withrespect to each other in a narrow space.

What is claimed is:

1. An actuator for a switch comprising a base portion adapted to besecured on a supporting frame, a first resilient member projectingforward from said base portion, a second resilient member extendingrearwardly from the forward free end of said first resilient member, andan actuating member secured at the free end of said second resilientmember, said first and second resilient members being so proportioned inlength, second moment of area and Youngs modulus that the actuatingmember performs a translational movement.

2. An actuator for a switch according to claim 1, in which the first andsecond resilient members are integral portions of a single stamped sheetof metal.

References Cited UNITED STATES PATENTS 2,627,002 1/1953 Alvarez 74-l002,755,346 7/1956 Fisher 200166 2,794,888 6/1957 Morse 200166 WESLEY S.RATLIFF, JR., Primary Examiner

